|Your Outdoor Project, Simplified.When to fertilize, what NPK ratios to use, county blackout dates, and fertilizer types — built specifically for St. Augustine, Zoysia, Bahia, and Bermuda grass on Florida's Gulf Coast.
Do NOT fertilize during the wet season blackout period. Most Gulf Coast counties (Sarasota, Manatee, Hillsborough, Pinellas, Charlotte) prohibit fertilizer applications from approximately June 1 – September 30. Violations carry fines and contribute directly to water quality problems across the region. Check your specific county's ordinance before any application.
Annual Applications
3–4
Best First Application
Mid-April
Blackout Period
Jun–Sep (most counties)
Final Application Deadline
October 31
Florida's fertilizer management is fundamentally different from the rest of the country — not just because of the climate, but because of legally enforced blackout periods, phosphorus restrictions, and water body proximity rules that apply across the Gulf Coast. The good news: if you follow the right schedule, Florida lawns are remarkably straightforward to maintain.
This guide covers the four annual application windows, fertilizer types that work best in Florida's alkaline sandy soils, county-by-county blackout dates for the Gulf Coast, and NPK recommendations for each major grass type.
Timing and product recommendations for Gulf Coast St. Augustine, Zoysia, Bahia, and Bermuda grass
1st Application
NPK Blend
15-0-15 or 16-4-8
Application Rate
1 lb N per 1,000 sq ft
Wait until grass is at least 80% green and actively growing. Applying too early to dormant grass wastes fertilizer and runs off. Slow-release nitrogen only.
2nd Application
NPK Blend
15-0-15 or iron-supplemented blend
Application Rate
1 lb N per 1,000 sq ft
Second application before the wet season fertilizer blackout begins (check your county's specific start date). Slow-release essential — fast-release in summer causes flush growth vulnerable to fungal disease.
CHECK BLACKOUT DATE — many counties begin June 1 or June 15. Do not apply within 2 days of predicted heavy rain.
Optional 3rd Application
NPK Blend
Minimal-nitrogen blend or iron only
Application Rate
0.5 lb N per 1,000 sq ft or iron supplement only
Only apply in counties/months where not restricted. Iron-only products are a legal alternative during blackout periods — they green the lawn without triggering growth flush. Milorganite is popular as a low-rate slow-release option.
Restricted in most coastal counties during summer wet season. Verify your county before any application.
Final Application
NPK Blend
0-0-22 or 4-0-8 (low N, high K)
Application Rate
1 lb K per 1,000 sq ft
The most important application many homeowners skip. High-potassium fall fertilizer hardens grass going into winter, improves cold tolerance, and strengthens disease resistance through the dry season. Apply by October 31 — many counties prohibit fertilizer after November 1.
Apply by Oct 31 — do NOT fertilize after this date until spring green-up.
Applying fertilizer during blackout periods is a legal violation. Fines start at $100 and escalate for repeat offenses.
What You Can Do During Blackout Periods
Iron Supplements
Chelated iron or iron sulfate is permitted and produces visible greening within 72 hours.
Organic Biosolids (Low N)
Milorganite and similar low-analysis organic products are permitted in many counties.
Nothing (the correct choice)
Florida lawns handle blackout periods fine. The wet season provides natural nutrients through atmospheric deposition.
Nitrogen, phosphorus, and potassium needs vary significantly between Florida's warm-season grass varieties
Nitrogen (N)
3–4
lbs/1,000 sq ft/yr
Phosphorus (P)
0
Not needed
Potassium (K)
2–3
lbs/1,000 sq ft/yr
Most susceptible to over-fertilizing — excess N causes thatch buildup and fungal disease in Florida's humidity.
Nitrogen (N)
2–3
lbs/1,000 sq ft/yr
Phosphorus (P)
0
Not needed
Potassium (K)
2
lbs/1,000 sq ft/yr
Lower nitrogen needs than St. Augustine. Over-fertilizing Zoysia causes excessive thatch that requires mechanical removal.
Nitrogen (N)
2–4
lbs/1,000 sq ft/yr
Phosphorus (P)
0
Not needed
Potassium (K)
1–2
lbs/1,000 sq ft/yr
Bahia has the lowest input requirements of Florida grasses. Yellowing is often iron deficiency — try iron supplement before adding N.
Nitrogen (N)
4–6
lbs/1,000 sq ft/yr
Phosphorus (P)
~
As needed
Potassium (K)
2–4
lbs/1,000 sq ft/yr
Bermuda has the highest nitrogen demand of Florida grasses. Only grass where split/frequent applications are appropriate.
Not all fertilizers behave the same in Florida's climate. Here's how each type performs in the heat, humidity, and sandy soils of the Gulf Coast.
Polymer-coated or sulfur-coated urea that releases nitrogen over 8–12 weeks. The Florida standard for residential lawn fertilization — reduces disease risk, prevents flush growth, and dramatically lowers nutrient runoff into waterways.
Common Products
Lesco 16-4-8, SunniLand 15-0-15, Lebanon 24-0-11
Pros
Cons
Water-soluble nitrogen (ammonium nitrate, urea, ammonium sulfate) that releases immediately. Produces fast visible greening but significantly higher runoff risk. Not recommended for residential Florida lawns — primarily used by commercial operations with precise equipment.
Common Products
Ammonium sulfate (21-0-0), plain urea (46-0-0)
Pros
Cons
Iron sulfate or chelated iron products that green lawns without adding nitrogen. The legal workaround during Florida's fertilizer blackout periods — you get a noticeable greening effect without violating restrictions. Chelated iron (EDTA or DTPA chelated) works better in alkaline Florida soils.
Common Products
Southern Ag Chelated Liquid Iron, Milorganite (low N organic), Ironite
Pros
Cons
Biosolid-based products (Milorganite is the most widely used) offer very slow nitrogen release and are typically permitted even during blackout periods in many Florida counties. Lower analysis means more product per 1,000 sq ft, but virtually zero burn risk and dramatically reduced runoff.
Common Products
Milorganite 6-4-0, Nature's Blend, compost tea
Pros
Cons
Common questions from Gulf Coast homeowners about fertilizing timing and compliance
Month-by-month mowing, irrigation, pest control, and fertilizing schedule for Gulf Coast lawns
Month-by-month sod installation timing for St. Augustine, Zoysia, and Bahia grass
Irrigation, drainage, storm prep, and seasonal care guides for Gulf Coast homeowners
Tampa Bay to Venice, FL Licensed Contractor Network Florida-Specific Expertise
The SunWest editorial team draws on direct field experience coordinating outdoor living, hardscape, and landscape projects across Sarasota, Manatee, Hillsborough, and Pinellas Counties — including barrier island work on Siesta Key, Longboat Key, and Anna Maria Island. Our content combines real project pricing, Florida code references, and material performance data to help Gulf Coast homeowners make better-informed decisions.
SunWest coordinates licensed lawn care professionals who know the county blackout dates, carry compliant products, and apply at the right rates for Gulf Coast soil conditions.
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